INAUGURAL ISSUE
Fermentations
in World
Food Processing
K.H. Steinkraus, Ph.D.
Professor Emeritus
Microbiology and Food Science
Cornell University
Ithaca, NY l4853
Introduction (Steinkraus 1995, 1996a, 1997)
Fermented foods are food substrates that are invaded or overgrown by edible microorganisms whose enzymes, particularly
amylases, proteases, lipases hydrolyze the polysaccharides, proteins and lipids to nontoxic products with flavors, aromas and textures pleasant and attractive to the human consumer. If the products of enzyme activities have unpleasant odors or undesirable,
unattractive flavors or the products are toxic or disease producing, the foods are described as spoiled.
Fermentation plays at least five roles in food processing:
(1) Enrichment of the human dietary through development of a
wide diversity of flavors, aromas and textures in food;
(2) Preservation of substantial amounts of food through lactic
acid, alcoholic, acetic acid, alkaline fermentations and high salt
fermentations;
(3) Enrichment of food substrates biologically with vitamins,
protein, essential amino acids and essential fatty acids;
(4) Detoxification during food fermentation processing and
(5) a decrease in cooking times and fuel requirements.
Classification of Food
Fermentations (Steinkraus 1995, 1997)
Food fermentations can be classified in a number of ways (Dirar
1993): by categories (Yokotsuka 1982)— (1) alcoholic beverages
fermented by yeasts; (2) vinegars fermented with Acetobacter; (3)
milks fermented with lactobacilli; (4) pickles fermented with lactobacilli; (5) fish or meat fermented with lactobacilli; and, (6) plant
proteins fermented with molds with or without lactobacilli and
yeasts; by classes (Campbell-Platt 1987) (1) beverages; (2) cereal
products; (3) dairy products; (4) fish products; (5) fruit and vegetable products; (6) legumes; and, (7) meat products; by commodity
(Odunfa 1988) (1) fermented starchy roots; (2) fermented cereals;
(3) alcoholic beverages; (4) fermented vegetable proteins; and, (5)
fermented animal protein; by commodity (Kuboye 1985) (1) cassava based; (2) cereal; (3) legumes; and, (4) beverages. Dirar
(1993) states that the Sudanese traditionally classify their foods,
not on the basis of microorganisms or commodity but on a functional basis: (1) Kissar (staples)-porridges and breads such as aceda and kissra; (2) Milhat (sauces and relishes for the staples); (3)
marayiss (30 types of opaque beer, clear beer, date wines and
meads and other alcoholic drinks); and, (4) Akil-munasabat (food
for special occasions). Steinkraus (1983a; 1996) classified fermentations according to the following categories that will serve as the
basis for this paper:
© 2002 Institute of Food Technologists
1. Fermentations producing textured vegetable protein meat
substitutes in legume/cereal mixtures. Examples are Indonesian
tempe and ontjom.
2. High salt/savory meat-flavored/amino acid/peptide sauce
and paste fermentations. Examples are Chinese soy sauce, Japanese shoyu and Japanese miso, Indonesian kecap, Malaysian kicap, Korean kanjang, Taiwanese inyu, Philippine taosi, Indonesian tauco, Korean doenjang/kochujang, fish sauces: Vietnamese
nuocmam, Philippine patis, Malaysian budu, fish pastes: Philippine bagoong, Malaysian belachan, Vietnamese mam, Cambodian prahoc, Indonesian trassi and Korean jeotkal. These are predominately Oriental fermentations but the use of these products is
becoming established in the United States.
3. Lactic acid fermentations. Examples of vegetable lactic acid
fermentations are: sauerkraut, cucumber pickles, olives in the
Western world; Egyptian pickled vegetables in the middle East; Indian pickled vegetables and Korean kim-chi, Thai pak-sian -dong,
Chinese hum-choy, Malaysian pickled vegetables and Malaysian
tempoyak. Lactic acid fermented milks include: yogurts in the
Western world, Russian kefir, Middle-East yogurts, liban (Iraq), Indian dahi, Egyptian laban rayab, laban zeer, Malaysian tairu (soybean milk). Lactic acid fermented cheeses in the Western world
and Chinese sufu/tofu-ru. Lactic acid fermented yogurt/wheat mixtures: Egyptian kishk, Greek trahanas, Turkish tarhanas. Lactic acid
fermented cereals and tubers (cassava): Mexican pozol, Ghanian
kenkey, Nigerian gari; boiled rice/raw shrimp/raw fish mixtures:
Philippine balao balao, burong dalag; lactic fermented/leavened
breads: sourdough breads in the Western world; Indian idli,
dhokla, khaman, Sri-lankan hoppers; Ethiopian enjera, Sudanese
kisra and Philippine puto; Western fermented sausages and Thai
nham (fermented fresh pork).
4. Alcoholic fermentations. Examples are grape wines, Mexican pulque, honey wines, South American Indian chicha and
beers in the Western World; wines and Egyptian bouza in the
Middle East; Palm and Jackfruit wines in India, Indian rice beer, Indian madhu, Indian ruhi; in Africa, Ethiopian tej, Kenyan muratina, palm wines, Kenyan urwaga, Kaffir/bantu beers, Nigerian pito,
Ethiopian talla, Kenyan busaa, Zambian maize beer; in the Far
East, sugar cane wines, palm wines, Japanese sake, Indonesian
tape, Malaysian tapuy, Chinese lao-chao, Thai rice wine, Indonesian brem, Philippine tapuy.
5. Acetic acid/vinegar fermentations. Examples are apple cider
and wine vinegars in the West; palm wine vinegars in Africa and
the Far East, coconut water vinegar in the Philippines; tea fungus/
Kombucha in Europe, Manchuria, Indonesia, Japan and recently
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in the United States; Philippine nata de pina and nata de coco.
6. Alkaline fermentations. Examples are Nigerian dawadawa,
Ivory Coast soumbara, African iru, ogiri, Indian kenima, Japanese
natto, Thai thua-nao.
7. Leavened breads. Examples are Western yeast and sourdough breads; Middle East breads.
8. Flat unleavened breads. The above classes of fermented
foods are found around the world. The lines between the various
classifications are not always distinct. Tempe in class 1 involves a
lactic acid fermentation during soaking of the soybeans. Yeast (alcoholic)/lactobacilli (lactic acid) interactions are rather frequentfor example in sourdough breads, in primitive beers and wines
and in Chinese soy sauce/Japanese shoyu/Japanese miso fermentations (Wood 1985). Nevertheless, Steinkraus (1983a, 1996) has
found the above classification useful and a way of predicting what
microorganisms may be involved and what chemical, physical
and nutritive changes may occur in new unfamiliar fermented
foods. The classification also relates well to safety factors found in
fermented foods.
Fermented foods were originally household and expanded to
cottage industry as consumer demand required. Some food fermentations such as Japanese shoyu, miso and sake, South African
maize/sorghum beers, South African mageu/mahewu Nigerian ogi
and gari have been industrialized (Steinkaus 1989).
Evolution of Indigenous
Fermented Foods (Steinkraus 1996a)
Philosophy includes theory or investigation of the principles or
laws that regulate the universe and underlie all knowledge and reality. Archaeology is the scientific study of the life and culture of
ancient peoples. Anthropology is the study of races, physical and
mental characteristics, distribution, customs, social relationships,
and so on. When we start to study man’s foods, we become involved in all the above. In fact, when we study fermented foods,
we are studying the most intimate relationships among man (men/
women-humans), microbes and foods. There is a never-ending
struggle between man and microbes to see which will be first to
consume the available food supplies.
Religion was an attempt by humans to explain the unexplainable origin of the universe, the earth and man long before there
was a scientific method or the means to study these difficult problems and no concept of, for example, microorganisms, knowledge of which we obtained only about 300 years ago when Leeuwenhoek discovered tiny animacules under his primitive lenses
and only a little more than a hundred years ago when Pasteur
demonstrated the role of microorganisms in fermentation and
Koch showed that microbes cause disease. And it is only in the
last 50 years that knowledge of the role polymeric deoxyribonucleic acid (DNA) plays in all forms of life was discovered.
According to present scientific thought, the earth is about 4.5
billion years old. The first forms of life to appear or evolve on
earth were microorganisms. Fossil organisms have been found in
earth rocks 3.3 to 3.5 billion years old (Schopf and Packer 1987).
Since then and still today, microorganisms have had and have the
principal task of recycling organic matter in the environment. As
such they are absolutely essential to the health of the earth,
whereas, humans are nonessential polluters who may eventually
make the earth uninhabitable.
Whether it was by chance or by design, it was extraordinarily
fortunate that the earth was originally colonized by microorganisms which are capable of recycling organic matter including
dead bodies, and so on. Without them, the earth would be a gigantic, permanent waste dump. The earth was inhabited by microorganisms for probably a billion years before other forms of life
24
evolved.
The next forms of life to evolve, according to present scientific
thought, were plants that serve as a basis for man’s food. For at
least a billion years before man arrived, plants were producing
food consisting of leaves, stems, seeds, nuts, berries, fruits, tubers,
and so on So when humans were created or evolved on earth, the
basis for their foods was already present and productive.
Both plants and animals evolved where the microbes were
ready, willing and able to recycle all organic matter. Plants and animals had to evolve into and survive in a microbial environment.
They had to develop ways of resisting microbial invasion and
consumption. Plants did this, in part, by having a lignocellulosic
body very resistant to microbial breakdown.
Until recently, we might have accepted the hypothesis that microorganisms, insects, animals, plants, humans were all created or
evolved independently. There was no good reason to believe that
all forms of life are closely interrelated. This changed when Watson and Crick unraveled the structure of DNA, the basis of the genetic code demonstrating that it is based upon a 4 molecule alphabet that controls the structure and function of all forms of life
including microorganisms, plants and all animals including man.
Early plant evolution was essential as plants not only provide
the basis for food for animals and man but they were principally
responsible for the development of the oxygen atmosphere necessary for man and animals.
Plants also introduced a very effective way of transforming the
sun’s radiation into food materials such as sugars, starches and
cellulose through the green pigment chlorophyll. Plants and plant
structures such as leaves, stems, roots and seeds all of which
serve as food for microorganisms and animals including ourselves are literally sun’s energy, radiation converted to matter.
Humans also had to evolve from the sea of microorganisms.
They had to develop internal and exterior systems of protection
against invasion by microorganisms. Then, as now some microorganisms could invade the live animal or human and cause disease. Animals including humans evolved with a “normal” flora of
microorganisms that live in the skin, mouth, throat, intestinal tract,
vagina, and so on. The normal flora protects us against invasion
by other microorganisms which might cause disease. Nowhere is
this more pronounced or more evident than in the human infant.
Within the uterus, the infant is essentially sterile but it can be
readily invaded by wide variety of microorganisms in the birth environment. The fact is, however, that, if the infant is breast-fed, as
nature intends, its intestinal tract becomes colonized by a particular species of bacteria, Bifidobacterium bifidus which produces
lactic acid and protects the infant against both intestinal and respiratory diseases. The skin of the human also is fairly resistant to invasion by undesirable microorganisms because of its “normal”
flora of cocci. Occasionally cocci may invade the skin and cause
infection but their role as “protectorants” is of much greater importance.
Early man very likely consumed fruits, leaves, berries, seeds,
nuts probably tubers foraging from place to place as apes do today. Their bodily wastes, as well as their bodies at death, were recycled by microorganisms. There was a relatively large potential
food supply and relatively few humans. Excess food supplies,
fruits, berries, fell on the ground and the seeds either germinated
or the carbohydrates, proteins, fats, and so on, were consumed
by microorganisms using enzymes that converted fermentable
carbohydrates to alcohol or acids and finally to water and carbon
dioxide. Seeds and nuts and other protein-containing components were converted to their essential amino acids, peptides and
finally to ammonia and water and a wide variety of chemical
products. All of these reactions occurred (as recycling) for a billion years before man arrived or evolved on earth.
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Fermentations in World Food Processing
As population increased it became desirable for humans to collect fruits, berries, nuts, seeds, leaves as a store of food to tide humans over during periods of bad weather (winter, for example)
when fresh food was not readily available.
Insects, rodents, birds and most types of animals were already
well-established on earth when man arrived. Food consumed by
insects or other animals is not available to man unless the insects
and animals are, in turn, consumed as food.
Foods invaded by bacteria producing toxins or by fungi producing mycotoxins are dangerous to man. If the products of invasion are ill-smelling, off-flavored or toxic, human consumers try to
avoid them and the foods are described as spoiled. If the microbial products are pleasantly flavored, have attractive aromas and
textures and are nontoxic, the human consumer accepts them
and they are designated as fermented foods.
Certain flavors such as sweet, sour, alcoholic and meat-like (savory) appeal to large numbers of humans. Milks sour naturally.
Fruit and berry juices rapidly become alcoholic. Over many centuries, people have developed tastes for such products that continue on in modern man. Some anthropologists have suggested
that it was stimulation and desire for alcohol that motivated man
to settle down and become agriculturists (Braidwood 1953; Katz
and Voight 1987).
Safety of Fermented Foods (Steinkraus 1995, 1997)
Fermented foods generally have a very good safety record even
in the developing world where the foods are manufactured by
people without training in microbiology or chemistry in unhygienic, contaminated environments. They are consumed by hundreds of millions of people every day in both the developed and
the developing world. And they have an excellent safety record.
What is there about fermented foods that contributes to safety?
While fermented foods are themselves generally safe, it should
be noted that fermented foods by themselves do not solve the
problems of contaminated drinking water, environments heavily
contaminated with human waste, improper personal hygiene in
food handlers, flies carrying disease organisms, unfermented
foods carrying food poisoning or human pathogens and unfermented foods, even when cooked if handled or stored improperly. Also improperly fermented foods can be unsafe. However, application of the principles that lead to the safety of fermented
foods could lead to an improvement in the overall quality and the
nutritional value of the food supply, reduction of nutritional diseases and greater resistance to intestinal and other diseases in infants.
Principles Behind Safety of Fermented Food Processes
The safety of food fermentation processes is related to several
principles.
The first is that food substrates overgrown with desirable, edible
microorganisms become resistant to invasion by spoilage, toxic or
food poisoning microorganisms. Other, less desirable (possibly
disease producing) organisms find it difficult to compete. An example is Indonesian tempe (Steinkraus 1996). The substrate is
soaked, dehulled, partially cooked soybeans. During the initial
soaking, the soybeans undergo an acid fermentation that lowers
the pH to 5.0 or below, a pH inhibitory to many organisms but
highly acceptable to the mold. Following cooking the soy cotyledons are surface dried which inhibits growth of bacteria that
might spoil the product. The essential microorganism is Rhizopus
oligosporus, or related Rhizopus species, which knit the cotyledons into a compact cake that can be sliced or cut into cubes and
used in recipes as a protein-rich meat-substitute. These molds
have the ability to grow very rapidly at relatively high temperatures, that is, 40 to 42 °C too high for many bacteria and molds.
The mold utilizes the available oxygen and produces CO2 which
inhibits some potential spoilage organisms. The mold also produces quantities of spore dust that permeate the environment and
contribute to inoculation of the desired microorganisms. The
combination of a relatively low pH, no free water and a high temperature in the fermenting bean mass enables Rhizopus oligosporus to overgrow the soybeans in 18 h. Organisms that might
otherwise spoil the product are unable to compete with the mold.
In addition, the mold also produces some antibiotic activity that
inhibits other organisms that might invade and spoil the product
(Wang and others 1969). The principle is that, as soon as the substrate is overgrown by the desired organism (s), it is resistant to invasion by other microorganisms. An additional safety factor is that
the raw tempe is sliced or cut into cubes and cooked before consumption which destroys vegetative microorganisms that are
present.
Soybean tempe (tempe kedelee) has an excellent record of safety in Indonesia and Malaysia where the product is fermented as
above and has been used for centuries. In temperate countries including the United States, soybeans do not undergo natural lactic
acid fermentation during soaking. The pH remains closer to 6.0 a
level that permits growth of contaminating bacteria. It has been
shown (Tanaka and others 1985) that unacidified soybeans can
be invaded by a variety of food poisoning organisms including
Staphylococcus aureus, Bacillus cereus and Clostridium botulinum. This can be prevented by artificially acidifying the soybeans
or inoculating the soak water with Lactobacillus plantarum ; but
American producers have often been careless and used unacidified beans or insufficiently acidified soybeans for tempe production. In some cases this has led to spoilage and could lead to food
poisoning.
While soybean tempe has an excellent safety record, there is a
type of tempe that has a reputation for causing sickness and even
death in the consumer. This is tempe bongkrek made from the coconut residue from coconut milk production. Again, if the substrate is properly acidified, it is generally safe and the mold overgrows the substrate knitting it into a compact cake. But, if the substrate is not sufficiently acidified and/or, if the fungal inoculum is
insufficient, a bacterium Burkholdaria (Pseudomonas) cocovenenans can grow in the coconut residue producing two toxic
compounds-bongkrek acid, the most lethal, and toxoflavin (Van
Veen 1967; Steinkraus 1996). These toxic compounds are inhibitory to the mold and it does not overgrow the substrate properly.
Bongkrek acid is colorless and it can be lethal to the consumer.
Toxoflavin is yellow and so, if tempe bongkrek has a yellow color
or if the mold has not overgrown the substrate properly, it should
not be consumed Yet, quite a number of Indonesians in central
Java die every year from consumption of improperly fermented
tempe bongkrek. This is an example of a fermented food that can
and does become toxic but it is amply documented and there is
no good excuse for people consuming it and becoming ill or dying.
It has been a mystery why bongkrek poison appears to develop
only in coconut tempeh fermented in Java. Part of the answer has
been discovered by Garcia, Hotchkiss and Steinkraus (1999). Forty and fifty percent coconut fat concentrations in the substrate (coconut presscake or the residue from coconut milk production)
supports production of 1.4 mg/g bongkrek acid while less than
10% coconut fat while, supporting growth of the bacterium,
yields no bongkrek acid. Oleic acid was most stimulatory in production of bongkrek acid (2.62 mg/g dry substrate). Lauric, myristic and palmitic acids also stimulated production of bongkrek acid
but at lower levels.
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A valid concern is mycotoxins that are present in many cereal
grain and legume substrates before fermentation. Aren’t these
dangerous to the consumer of fermented foods? Certainly they are
a problem; however, it is not the fermentation that produces mycotoxins. They are produced when the cereal grains or legumes are
improperly harvested or stored. It has been found that in the
tempe fermentation, mycotoxin levels are reduced. Van Veen and
others (1970) reported that the ontjom mold, Neurospora and the
tempe mold Rhizopus oligosporus could decrease the aflatoxin
content of peanut presscake 50% and 70% respectively during
fermentation. And during soaking and cooking of raw substrates
before fermentation, many potential toxins such as trypsin inhibitor, phytate and hemagglutinin are destroyed. So, in general, fermentation tends to detoxify the substrates.
Sudigbia and Sumantri (1990) developed an infant formula
containing tempe as 39.6% of its weight. Other major ingredients
were wheat flour 31.6%, sugar 23.3% and vegetable oil 2.9%. Infants suffering from acute diarrhea and consuming the formula recovered more rapidly than infants not receiving the formula and
also gained weight rapidly. It would appear that inclusion of
tempe in infant formulas on a broader scale would not only decrease the overall incidence of diarrhea but also improve infant/
child growth rates and nutrition.
Lactic acid fermentations
A second principle is that fermentations involving production
of lactic acid are generally safe. Lactic acid fermentations include
those in which the fermentable sugars are converted to lactic acid
by lactic acid organisms such as Leuconostoc mesenteroides,
Lactobacillus brevis, Lactobacillus plantarum, Pediocccus cerevisiae, Streptococcus thermophilus, Streptococcus lactis, Lactobacillus bulgaricus, Lactobacillus acidophilus, Lactobacillus citrovorum, Bifidobacterium bifidus, and so on.
This single category is responsible for processing and preserving vast quantities of human food and insuring its safety. We are
all aware of the excellent safety record of sour milks/yogurts,
cheeses, pickles, and so on. In addition the lactic acid fermentations provide the consumer with a wide variety of flavors, aromas
and textures to enrich the human diet.
The most ancient lactic fermentation, likely, is fermented/sour
milk. Raw, unpasteurized milk will rapidly sour because the lactic
acid bacteria present in the milk ferment milk sugar, lactose to lactic acid. In the presence of acid and a low pH, other microorganisms that might invade the milk and transmit disease-producing
organisms are less able to do so.
If the whey is allowed to escape or evaporate, the residual curd
becomes a primitive cheese. Fermented cheeses and milks are an
extensive topic on their own (Kosikowski 1977; Wood, 1998).
The readers are referred to Dr. Kosikowski’s classic book “Cheese
and Fermented Milk Foods” for details.
Vegetable foods and vegetable/fish/shrimp mixtures are preserved around the world by lactic acid fermentation (Steinkraus
1983a,c; 1996). The classic lactic acid/vegetable fermentation is
sauerkraut (Pederson and Albury 1969; Pederson 1979). Fresh
cabbage is shredded and 2.25% salt is added. There is a sequence of lactic acid bacteria that develop. First, Leuconostoc
mesenteroides grows producing lactic acid, acetic acid and CO2
which flushes out any residual oxygen making the fermentation
anaerobic. Then Lactobacillus brevis grows producing more acid.
Finally Lactobacillus plantarum grows producing still more lactic
acid and lowering the pH to below 4.0. At this pH and under
anaerobic conditions, the cabbage or other vegetables will be
preserved for long periods of time.
Korean kimchi is a fermentation similar to sauerkraut but it in26
cludes not only Chinese cabbage but radishes, red pepper, ginger
and garlic. It is less acid than sauerkraut and is consumed while
still carbonated. It is a staple and makes a major contribution to
the Korean diet in which consumption of 100 g or more/capita/
day is not uncommon (Mheen and others 1977; Steinkraus 1983
a,c). Kimchi is still a household fermentation in Korea although it
can be purchased commercially.
Pickled vegetables, cucumbers, radishes, carrots and very nearly all vegetables and even some green fruits such as olives, papaya and mango are acid fermented in the presence of salt around
the world. Mukerjee (1987) demonstrated that Indian farmers can
safely preserve their surplus vegetables by lactic acid fermentation
on the farm. This improves the supply and availability of vegetable
foods throughout the year and improves the nutrition of the Indian population.
Pit fermentations
Lactic acid fermentations include the “pit” fermentations in the
South Pacific Islands. They have been used for centuries by the
Polynesians to store and preserve breadfruit, taro, banana and
cassava tubers (Steinkraus 1986; Aalbersberg and others 1988).
The fermented pastes or whole fruits, sometimes punctured, are
placed in leaf-lined pits. The pits are covered with leaves and the
pits are sealed. It has recently been found that pit fermentations
are lactic acid fermentations (Aalbersberg and others 1988) The
low pH and anaerobic conditions account for the stability of the
foods. An abandoned pit estimated to be about 300 years old
contained breadfruit still in edible condition.
In Ethiopia, pulp of the false banana (Ensete ventricosum) is
also fermented in pits (Steinkraus 1983a). It undergoes lactic acid
fermentation and is preserved until the pit is opened. Then the
mash is used to prepare a flat bread kocho-a staple in the diet of
millions of Ethiopians.
Lactic acid fermented rice/shrimp/fish mixtures
Philippine balao balao is a lactic acid fermented rice/shrimp
mixture prepared by mixing boiled rice, raw shrimp and solar salt
(about 3% w/w), packing in an anaerobic container and allowing
the mixture to ferment over several days or weeks (Arroya and
others 1977); Steinkraus 1883a,c). The chitinous shell of the
shrimp becomes soft and when the product is cooked, the whole
shrimp can be eaten. The process provides a method of preserving raw shrimp or pieces of raw fish (burong dalog) (Orillo and
Pederson 1968). The products are well-preserved by the low pH
and anaerobiosis until the containers are opened. Then they must
be cooked and consumed.
Yogurt/cereal mixtures
Another household lactic acid fermentation of considerable nutritional importance includes Egyptian kishk, Greek trahanas and
Turkish tarhanas. These products are basically parboiled wheat/
yogurt mixtures that combine the high nutritional value of wheat
and milks while attaining excellent keeping qualities. The processes are rather simple. Milk is fermented to yogurt and the yogurt
and wheat are mixed and boiled together until the mixture is highly viscous. The mixture is than allowed to cool, formed into biscuits by hand and sun-dried. Trahanas can be stored on the kitchen shelf for years and used as a base for highly nutritional soups.
In the Egyptian kishk process, tomatoes, onions and other vegetables are sometimes combined with the yogurt and wheat in the
biscuits (Abd-el-Malek and Demerdash 1977; Steinkraus
1983a;1996).
Cereal/legume sour gruels/porridges/beverages
Cereal/legume sour gruels/porridges/beverages include Nigeri-
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Fermentations in World Food Processing
an ogi, Kenyan uji, South African mahewu/magou, and Malaysian
soybean milk yogurt (tairu). In Nigerian ogi, maize, millet or sorghum grains are washed and steeped for 24 to 72 h during which
time they undergo lactic acid fermentation. They are drained, wet
milled and finally wet-sieved to yield a fine, smooth slurry with
about 8% solids content. The boiled slurry called “pap”, is a porridge. Pap is a very important traditional food for weaning infants
and a major breakfast food for adults. Infants 9 months old are introduced to ogi by feeding once a day as a supplement to breast
milk (Steinkraus 1983a; Banigo 1969; Banigo and Muller 1972).
Unfortunately the nutritional value of ogi is poor. It is vastly improved by the addition of soybean to produce a soy-ogi (Akinrele
and others 1970).
Kenyan uji is a related product except that the grains are
ground to a flour before mixing with water and fermenting. The
initial slurry is 30% solids. This is fermented for 2 to 5 days yielding 0.3 to 0.5% lactic acid. The slurry is then diluted to 10% solids and boiled. It is then diluted to 4 to 5% solids and 6% sucrose
is added for consumption (Dirar 1993; Steinkraus 1983a; Gatumbi and Muriru 1987; Mbugua 1981)).
South African mageu/mahewu/magou is a traditional sour, nonalcoholic maize beverage popular among the Bantu people of Africa (Holzapfel 1989). Corn flour is slurried with water (8 to 10%
solids), boiled, cooled and inoculated with 5% w/w wheat flour
(household fermentation) which serves as a source of microorganisms and incubated at ambient temperature or the boiled slurry is inoculated with Lactobacillus delbrueckii (industrial process)
and incubated at 45 C. The slurries are fermented to a pH of 3.5 to
3.9 and then are ready for consumption.
Lorri (1993) and Svanberg and others (1992) reported that lactic acid-fermented gruels inhibited the proliferation of
Gram-negative pathogenic bacteria including toxicogenic Escherichia coli, Campylobacter jejuni, Shigella flexneri and Salmonella
typhimurium. The mean number of diarrhea episodes in preschool children over a 9 month period was 2.1 per child using
fermented gruels compared with 3.5 per child using
non-fermented gruels. Lorri also reported that using a natural lactic acid culture and flour of germinated seeds (power flour), it was
possible to prepare liquid cereal gruels from maize, white sorghum, bulrush millet and finger millet with a 30 to 35% flour concentration. The energy density of such a lactic acid-fermented gruel was about 1.2 kcal/g, as compared with 0.4 kcal/g in a
non-fermented gruel prepared to the same consistency. This is a
3-fold increase in energy density. Also, the in vitro protein digestibility of high-tannin cereal varieties was significantly increased
from a range of 32 to 40% before fermentation to a range of 41 to
60% after lactic acid-fermentation. Lactic acid fermentation of
non-tannin cereals with added flour of germinated sorghum grain
or wheat phytase increased iron solubility from about 4% to 9%
and 50% respectively. Thus lactic acid fermentation has very profound effects on the nutritive value of cereal gruels for feeding infants and children in the developing world.
Ingestion of foods containing live lactic acid bacteria is likely to
improve the resistance of the gastrointestinal tracts of infants and
children to invasion by organisms causing diarrhea.
Cereal/legume steamed breads and pancakes
Indian idli, a sour, steamed bread, and dosa, a pancake are examples of a household fermentation that could be useful around
the world. Polished rice and black gram dahl in various proportions, that is, 3:1 to 1:3 are soaked by the housewife separately
during the day. In the evening, the rice and black gram are ground
in a mortar and pestle with added water to yield a batter with the
desired consistency. The batter is thick enough to require the use
of the hand and forearm to mix it properly. A small quantity of salt
is added. The batter ferments overnight during which time Leuconostoc mesenteroides and Streptococcus faecalis, naturally
present on the grains/legumes/utensils grow rapidly outnumbering the initial contaminants and dominating the fermentation. The
organisms produce lactic acid (total acidity as lactic can reach
above 1.0%) and carbon dioxide that makes the batter anaerobic
and leavens the product. In the morning, the batter is steamed to
produce small white muffins or fried as a pancake. Soybean cotyledons, green gram, Bengal gram can be substituted for the black
gram. Wheat, maize or kodri can be substituted for the rice to
yield Indian dhokla (Ramakrishnan 1979a, 1979b; Steinkraus
1983a; 1996). A closely related fermentation is Ethiopian enjera
that yields the large pancake that serves as the center of the meal.
Alcoholic fermentations
A third principle contributing to food safety is that fermentations
involving production of ethanol are generally safe foods and beverages (Steinkraus 1979). These include wines, beers, Indonesian
tape ketan/tape ketella, Chinese lao-chao, South African kaffir/sorghum beer and Mexican pulque. These are generally yeast fermentations but they also involve yeast-like molds such as Amylomyces rouxii and mold-like yeasts such as Endomycopsis and
sometimes bacteria such Zymomonas mobilis. The substrates include diluted honey, sugarcane juice, palm sap, fruit juices, germinated cereal grains or hydrolyzed starch all of which contain
fermentable sugars that are rapidly converted to ethanol in natural
fermentations by yeasts in the environment. Nearly equal weights
of ethanol and carbon dioxide are produced and the CO2 flushes
out residual oxygen and maintains the fermentation anaerobic.
The yeasts multiply and ferment rapidly and other microorganisms most of which are aerobic cannot compete. The ethanol is
germicidal and, as long as the fermented product remains anaerobic, the product is reasonably stable and preserved.
With starchy substrates such as cereal grains, it is necessary to
convert some of the starch to fermentable sugar. This is done in a
variety of ways, that is, chewing the grains to introduce ptyalin
(Andes region of South America) where maize is a staple or germination (malting) of barley or the grains themselves in most of the
world where beers are produced. In parts of Africa, a young lady
cannot get married until she is capable of making Bantu beer for
her husband.
In Asia, there are at least two additional ways of fermenting
starchy rice to alcoholic foods. The first is the use of a mold such
as Amylomyces rouxii which produces amylases converting
starch to sugars and a yeast such as Endomycopsis fibuliger
which converts the glucose/maltose to ethanol. The sweet sour/ alcoholic product of rice fermentation is called tape ketan in Indonesia. It is consumed as a dessert. When cassava is used as substrate, the product is called tape ketella (Merican and Yeoh 1989;
Steinkraus 1983a). This process can also be used to produce rice
wines, Chinese lao-chao and Malaysian tapuy/tapai.
Another method is the Japanese koji process used to ferment rice
to rice wine (sake) (Yoshizawa and Ishikawa 1989; Steinkraus
1979b; 1983a). In this process, boiled rice is overgrown with an
amylolytic mold Aspergillus oryzae for about 3 days at 30 C. The
mold-covered rice called a “koji” is then inoculated with a culture
of the yeast Saccharomyces cerevisiae and water is added. Saccharification by the mold amylases and alcoholic fermentation by the
yeast proceed simultaneously. The result of slow fermentation is
high yeast populations and ethanol contents as high as 23% v/v.
Acetic acid/vinegar fermentation
If the products of alcoholic fermentation are not kept anaerobic,
Vol. 1, 2002—COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY 27
CRFSFS: Comprehensive Reviews in Food Science and Food Safety
bacteria belonging to genus Acetobacter present in the environment oxidize portions of the ethanol to acetic acid/vinegar (Conner and Allgier 1976; Steinkraus 1983a;1996).
Fermentations involving production of acetic acid yield foods
or condiments that are generally safe. Acetic acid also is bacteriostatic to bactericidal depending upon the concentration. In most
cases, palm wines and kaffir beers contain not only ethanol but
acetic acid. Acetic acid is even more preservative than ethanol.
Vinegar is a highly acceptable condiment used in pickling and
preserving cucumbers and other vegetables. The alcoholic and
acetic acid fermentations can be used to insure safety in other
foods.
Over the last few years, the American public has become aware
of a fermented acetic acid beverage called kombucha or tea fungus. Actually kombucha has been known and produced for a
long period of time historically in China, Russia and Germany
(Steinkraus and others 1996; Greenwalt and others 1998; 2000).
The fermentation involves sweetened (5 to 15% sugar) tea infusion and a microbial mat containing Acetobacter and a variety of
yeasts that grows on the surface of the substrate producing primarily acetic and gluconic acids in approximately equal quantities
(above 3% total). pH is about 2.5. While various
health-promoting qualities have been ascribed to kombucha, the
fact appears to be that the acetic acid is the primary microbial inhibitor and, if it is consumed in too large quantities, it can cause
indigestion and even death.
Leavened Bread Fermentation
Yeast breads are closely related to the alcoholic fermentation
and have an excellent reputation for safety. Ethanol is a minor
product in bread because of the short fermentation time; but carbon dioxide produced by the yeasts leavens the bread producing
anaerobic conditions and baking produces a dry surface resistant
to invasion by organisms in the environment. Baking also destroys many of the microorganisms in the bread itself.
Yeast breads are made by fermentation of wheat and rye flour
doughs with yeasts, generally Saccharomyces cerevisiae (Sugihara
1985). Sour dough breads are fermented with lactic acid bacteria
and yeasts; Indian idli/dosa-rice/legume mixtures are fermented
with Leuconostoc mesenteroides and Streptococcus faecalis and
sometimes added yeasts (see lactic acid fermentations above).
Alkaline Fermentations
Fermentations involving highly alkaline fermentations are generally safe. Africa has a number of very important foods/condiments
that are not only used to flavor soups and stews but also serve as
low-cost sources of protein in the diet (Odunfa 1988). Among
these are Nigerian dawadawa, Ivory cost soumbara and West African iru made by fermentation of soaked, cooked locust bean
Parkia biglobosa seeds with bacteria belonging to genus Bacillus,
typically Bacillus subtilis. Nigerian ogiri made by fermentation of
melon seed (Citrullus vulgaris); Nigerian ugba made by fermentation of the oil bean (Pentacletha macrophylla); Sierra Leone
ogiri-saro made by fermentation of sesame seed (Sesamum indicum); Nigerian ogiri-igbo made by fermentation of castor bean
(Ricinus communis) seeds and Nigerian ogir-nwan made by fermentation of the fluted pumpkin bean (Telfaria occidentale) seeds.
Soybeans can be substituted for locust beans. (Steinkraus 1991).
This group also includes Japanese natto, Thai thua-nao and Indian kenima all based upon soybean.
The essential microorganisms are Bacillus subtilis and related
bacilli. The organisms are very proteolytic and the proteins are hydrolyzed to peptides and amino acids. Ammonia is released and
28
the pH rapidly reaches as high as 8.0 or higher. The combination
of high pH and free ammonia along with very rapid growth of the
essential microorganisms at relatively high temperatures-above 40
°C (recall principle 1) make it very difficult for other microorganisms that might spoil the product to grow. Thus, the products are
quite stable and well-preserved especially when dried. They are
safe foods even though they may be manufactured in an unhygienic environment.
These are all household fermentations that depend upon Bacillus subtilis spores in the environment. No deliberate inoculum is
needed. The seeds are soaked and the seed-coats are removed.
The seeds are then cooked and drained. Shallow pots or pans are
used for the fermentation. The pans are sources of the required
spores, which germinate and overgrow the seeds forming a sticky
mucilaginous gum on the surfaces of the beans/seeds.
They are very nutritious and a source of low-cost nitrogen for
the diet.
Interestingly, the Malaysians ferment locust beans by a similar
alkaline process to yield garlic flavored products. The Japanese
ferment soybeans with Bacillus subtilis after soaking and cooking
to yield a protein-rich food called natto. The Thais also ferment
soybeans by a similar process to produce a product called
thua-nao consumed in Northern Thailand as a substitute for fish
sauce. The Indians also ferment soybeans by similar processes to
produce kenima. Thus, these alkaline fermentations involving bacilli fermenting protein rich beans and seeds are of considerable
importance in widely separated parts of the world. They are all
household fermentations but Japanese natto has been commercialized (Steinkraus 1991).
High Salt Savory Flavored Amino/Peptide Sauces and
Pastes
Addition of salt in ranges from 13% w/v or higher to
protein-rich substrates results in a controlled protein hydrolysis
that prevents putrefaction, prevents development of food poisonings such as botulism and yields meaty, savory, amino acid/peptide sauces and pastes that provide very important condiments
particularly for those unable to afford much meat in their diets.
Meaty/savory flavored amino acid/peptide sauces and pastes
include Chinese soy sauce/Japanese shoyu/Japanese miso/Indonesian kecap/ Taiwan inyu/Korean kan-jang/Philippine taosi made
by fermentation of soybeans or soybean/rice-barley mixtures with
Aspergillus oryzae and fish sauces and pastes made by fermentation of small fish and shrimp using principally the proteolytic gut
enzymes of the fish and shrimp (Fukashima 1989; Ebine 1989;
Steinkraus 1983a,b; 1989).
The ancient discovery of how to transform bland vegetable protein into meat-flavored amino acid/peptide sauces and pastes was
an outstanding human accomplishment. Like many discoveries, it
was probably initially accidental. The earliest substrates were likely meat or fish mixed with a millet koji (Fukashima 1989).
In the most primitive process known today, soybeans are
soaked and thoroughly cooked (Shurtleff and Aoyagi 1976). They
are mashed, formed into a ball, covered with straw and hung to
ferment under the rafters of the house. In 30 days they are completely overgrown with the mold Aspergillus oryzae. Packed into a
strong salt brine (about 18% w/v) the beans are hydrolyzed by the
proteases, lipases and amylases in the mold yielding an amino
acid/peptide liquid sauce with a meaty flavor and a similar
meat-flavored paste/residue-a primitive miso. One can only guess
what a dramatic effect this meat-flavored sauce and paste had on
consumers of the typical bland rice diet in the Orient. The process
not only enriches the flavor but it also contains the essential amino acids in the soybean. Because of the relatively high lysine con-
COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY—Vol. 1, 2002
Fermentations in World Food Processing
tent of the soybean, soy sauce/miso is an excellent adjunct to the
nutritional quality of rice. Soy sauce started as an Oriental food;
but, in recent years it has been adopted by the West, particularly
the Americans.
In the presence of high salt concentration (above 13% w/v and
generally in the range of 20 to 23%) fish gut enzymes will hydrolyze fish proteins to yield amino acid/peptide, meaty flavored fish
sauces and pastes similar to soy sauces/pastes. Halophilic pediococci contribute to the typical desirable fish sauce flavor/aroma.
Both soy sauce and fish sauce fermentations are carried out at the
household level as well as by large commercial manufacturers.
In summary, food fermentations that improve food safety are as
follows:
1. Food substrates rapidly overgrown by edible microorganisms
leading to desirable flavors, aromas and free of toxins are resistant
to development of spoilage, food poisoning or toxin-producing
organisms.
2. Food fermentations involving lactic acid production
3. Food fermentations involving ethanol production
4. Food fermentations involving acetic acid production
5. Food fermentations involving highly alkaline conditions with
liberation of free ammonia
6. Food fermentations carried out in the presence of high salt
concentrations (above 13% w/w) are generally safe.
Nutritional Aspects of Fermented Foods
“Nutrition” or “nutritional” is the supplying of calories/energy.
Protein, essential amino acids/peptides, essential fatty acids and
vitamins and mineral requirements to satisfy metabolic needs of
the consumer (Steinkraus 1994, 1995, 1997).
Two major food problems exist in the world. Starvation (or
under-nutrition where there is insufficient food or insufficient economic means to provide the necessary food) and obesity (or
over-consumption of food in the wealthy, developed world).
There is outright starvation and death in countries such as Ethiopia, Sudan, Somalia and Bangladesh due to poverty, drought, environmental disasters and war combined with lack of economic
means to purchase food.
There are a number of nutritional diseases in the developing
world today. Kwashiorkor, the result of protein deficiencies, and
marasmus, caused by a combination of protein and calorie deficiencies, are found in large numbers of children between the ages
of 1 and 3 in the developing world. The immune systems of the
children are impaired on restricted protein diets. Such children often develop diarrhea and the mothers place them on restricted diets such as rice broth. Since the children are already deficient in
protein, they quickly develop kwashiorkor with tissue edema,
bloated abdomens, susceptibility to infection and changes in hair
pigments. Kwashiorkor can develop in children consuming sufficient calories if their protein is deficient. On the other hand marasmus is the result of both calorie and protein deficiencies in children under 1 years of age due to early cessation of breast-feeding
and the attempted replacement with artificial milks with very dilute
protein contents (Jelliffe 1968). The principal features of marasmus
are growth retardation, muscle wasting and loss of subcutaneous
fat. Both kwashiokor and marasmus can result in mental retardation if the child survives.
Other nutritional diseases common in the developing world are
xerophthalmia, childhood blindness due to vitamin A deficiency;
beri-beri due to thiamine deficiency including infantile beri-beri
where sudden death may occur from heart failure in children being nursed by mothers deficient in thiamine; pellagra due to niacin deficiency, riboflavin deficiency; rickets cause by vitamin D
deficiency; anemia due to vitamin B-12 deficiency or insufficient
iron in the diet (Jelliffe 1968).
The nutritional impact of fermented foods on nutritional diseases can be direct or indirect. Food fermentations that raise the protein content or improve the balance of essential amino acids or
their availability will have a direct curative effect. Similarly fermentations that increase the content or availability of vitamins such as
thiamine, riboflavin, niacin or folic acid can have profound direct
effects on the health of the consumers of such foods. This is particularly true of people subsisting largely on maize where niacin
or nicotinic acid is limited and pellagra is incipient and in people
subsisting principally on polished rice which contains limited
amounts of thiamine and beri-beri is incipient (Jelliffe 1968). Biological enrichment of foods via fermentation can prevent this.
On the other hand, fermentation does not generally increase
calories unless they convert substrates unsatisfactory for humans
to human quality foods such as mushrooms produced on straw
or waste paper or converting peanut and coconut presscakes to
edible foods such as Indonesian ontjom (oncom).
While the Western world can afford to enrich its foods with
synthetic vitamins, the developing world must rely upon biological enrichment for its vitamins and essential amino acids. The affluent Western world cans and freezes much of its food but the
developing world must rely upon fermentation, salting and solar
dehydration to preserve and process its foods at costs within the
means of the average consumer. All consumers today have a considerable portion of their nutritional needs met through fermented
foods and beverages. This is likely to expand in the 21st century
when world population reaches 8 to 12 billion (Steinkraus 1994).
Biological Enrichment by Fermentation (Steinkraus,1998)
Enrichment with protein
In the Indonesian tape ketan fermentation referred to earlier,
rice starch is hydrolyzed to maltose and glucose and fermented to
ethyl alcohol. The loss of starch solids results in a doubling of the
protein content (from about 8% to 16% in rice) on a dry solids
basis (Cronk and others 1977). Thus, this process provides a
means by which the protein content of high starch substrates can
be increased for the benefit of consumers needing higher protein
intakes. This is particularly important for people consuming principally cassava which has a protein content of about 1% (wet basis). If the tape ketella fermentation is applied to cassava as it is in
Indonesia, the protein content can be increased to at least 3%
(wet basis) - a very significant improvement in nutrition to the consumer. In addition, the flavor of the cassava becomes sweet/sour
and alcoholic, flavors consumers may prefer to the bland starting
substrate.
Bio-enrichment with essential amino acids
The Indonesian tape ketan/tape ketella fermentation not only
enriches the substrate with protein, the microorganisms also selectively enrich the rice substrate with lysine, the first essential limiting amino acid in rice (Cronk and others 1977). This improves
the protein quality.
Several researchers have reported from 10.6 to 60.0% increases in methionine during the Indian idli fermentation. (Rao 1961;
Rajalakshmi and Vanaja 1967; Steinkraus and others 1967). An
increase in methionine, a limiting essential amino acid in legumes
greatly improves the protein value.
Bio-enrichment with vitamins
In the wealthy, Western world, nutrients particularly vitamins
are added to selected, formulated, manufactured foods as a public health measure. Examples are addition of vitamin D to milk, vitamin A and D to milk and butter and riboflavin to bread. Fruit
Vol. 1, 2002—COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY 29
CRFSFS: Comprehensive Reviews in Food Science and Food Safety
juices may be fortified with ascorbic acid (vitamin C). While enrichment/fortification are within the means of the Western World,
they are far beyond the means of the developing world. Thus,
much of the world must depend upon biological enrichment via
fermentation to enrich their foods (Steinkraus 1985).
Highly polished white rice is deficient in vitamin B-1 (thiamine).
Consumers subsisting principally on polished rice are in danger
of developing beri-beri, a disease characterized by muscular
weakness and polyneuritis leading eventually to paralysis and
heart failure (Robinson 1972). Infants being nursed by mothers
suffering from thiamine deficiency may develop infantile beri-beri
in which sudden death occurs at about 3 months of age due to
cardiac failure (Jelliffe 1968). The microorganisms involved in the
tape ketan fermentation synthesize thiamine and restore the thiamine content to the level found in unpolished rice (Cronk and
others 1977) This can be a very significant contribution to the nutrition of rice eating people.
Tempe is a protein-rich meat substitute in Indonesia made by
overgrowing soaked, dehulled, partially cooked soybeans with
Rhizopus oligosporus or related molds (Steinkraus 1983a). The
mold knits the cotyledons into a firm cake that can be sliced and
cooked or used in place of meat in the diet. During the fermentation, proteins are partially hydrolyzed, the lipids are hydrolyzed to
their constituent fatty acids, stachyose (a tetrasaccharide indigestible in humans) is decreased decreasing flatulence in the consumer,
riboflavin nearly doubles, niacin increases sevenfold and vitamin
B-12 usually lacking in vegetarian foods is synthesized by a bacterium that grows along with the essential mold (Liem and others
1977; Steinkraus 1983a, 1985). The tempe process can be used to
introduce texture into many legume/cereal mixtures yielding products with decreased cooking times and improved digestibility. The
bacterium responsible for the vitamin B-12 production is a nonpathogenic strain of Klebsiella pneumoniae. When inoculated into
the Indian idli fermentation, it also produces vitamin B-12.
Mexican pulque is the oldest alcoholic beverage on the American continent. It is produced by fermentation of juices of the cactus plant (Agave) (Steinkraus 1983a, 1979b). Pulque is rich in thiamine, riboflavin, niacin, panthothenic acid, p-amino benzoic
acid, pyridoxine and biotin (Sanchez-Marroquin 1977). Pulque is
of particular importance in the diets of the low-income children of
Mexico.
Kaffir beer is an alcoholic beverage with a pleasantly sour taste
and the consistency of a thin gruel (Steinkraus 1983a, 1989). It is
a traditional beverage of the Bantu people of South Africa. Alcohol content ranges from 1 to 8% v/v. Kaffir beer is generally made
from kaffircorn (Sorghum caffrorum) malt and unmalted kaffircorn
meal. Maize or millet may be substituted for kaffircorn. During the
fermentation, thiamine remains about the same, but riboflavin
more than doubles and niacin/nicotinic acid nearly doubles,
which is very significant in people consuming principally maize.
Consumers of usual amounts of kaffir beer are not in danger of
developing pellagra.
Palm sap is a sweet, clear, colorless liquid containing about 10
to 12% fermentable sugar and neutral in reaction (Okafor 1975);
Steinkraus 1979b). Palm wine is a heavy, milk-white opalescent
suspension of live yeasts and bacteria with a sweet taste and vigorous effervescence. Palm wines are consumed throughout the
tropics. Palm wine contains as much as 83 mg ascorbic acid/liter
(Bassir 1968). Thiamine increased from 25 ug to 150 ug/liter, riboflavin increased from 35 to 50 ug/liter and pyridoxine increased
from 4 to 18 ug/liter during fermentation. Surprisingly, palm wine
contains considerable amounts of vitamin B-12, 190 to 280 pg/ml
(Van Pee and Swings, 1971). Palm toddies play an important role
in nutrition among the economically disadvantaged in the tropics.
They are the cheapest sources of B vitamins.
30
Reduction of toxins
During soaking and hydration that raw substrates undergo in
various fermentation processes and the usual cooking, many potential toxins such as trypsin inhibitor, phytate and hemagglutinin
and cyanogens in cassava are reduced or destroyed. Even aflatoxin, frequently found in peanut and cereal grains substrates is reduced in the Indonesian ontjom fermentation (Steinkraus, 1983a).
Van Veen and others (1968) found that the ontjom mold, Neurospora and the tempe mold Rhizopus oligosporus could decrease
the aflatoxin content of peanut presscake 50% and 70% respectively during fermentation.
Reduction of cooking times
Economy of fuel requirements is very important in the developing world where housewives may spend hours every day collecting enough leaves, twigs, wood and dried dung to cook the day’s
food. Lactic-acid fermented foods generally require little, if any,
heat in their fermentation and can be consumed without cooking.
Examples are pickled vegetables, sauerkraut, kimchi. Indonesian
tempe fermentation converts soybeans that would require as
much as 5 to 6 h cooking to a product that can be cooked in
soup with 5 to 10 min boiling (Steinkraus 1983a).
Summary
Fermented foods provide and preserve vast quantities of nutritious foods in a wide diversity of flavors, aromas, and textures
which enrich the human diet. Fermented foods have been with us
since humans arrived on earth. They will be with us far into the future, as they are the source of alcoholic foods, beverages, vinegar,
pickled vegetables, sausages, cheeses, yogurts, vegetable protein
amino acid/peptide sauces and pastes with meat-like flavors, and
leavened and sourdough breads. All consumers today have a
considerable portion of their nutritional needs met through fermented foods and beverages. This is likely to expand in the 21st
century, when world population reaches 8 to 12 billion.
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